1. Field of the Invention
The present invention concerns a cement- and additive-based binder which, mixed in combination with aggregates of carefully selected particle size on the one hand, and with mixing water on the other hand, allows a very fluid, easy-to-use, paste to be obtained, characterized by the fact that the paste is self-smoothing, self-levelling and presents hardly any shrinkage after the setting of the cement.
2. Discussion of Background Information
The traditional techniques for constructing screeds and slabs using hydraulic binders based on artificial cements, standard quality aggregates and water, are well known. The pastes thus obtained, of variable consistency, are generally applied to rough substrates and take several hours to set, after hydration of the cement, and produce flat, smooth surfaces at the cost of numerous difficult secondary operations carried out after the cement has been spread. It is well known that such pastes are normally relatively firm and even plastic, and the handling of these pastes, whether mixing, transport, spreading or smoothing, can be partially mechanized or entirely manual, in accordance with techniques perfectly known to the tradesman.
It is also known that the mechanical characteristics of structures obtained using such binders, even if they correspond to standards in force, lack reliability in the long term, and it is very commonly observed that many structures suffer major damage during the ten-year guarantee period, notably due to the considerable hydraulic shrinkage and the low mechanical strengths resulting from these traditional mixes. It will also be noted that, because of these technical problems, it is often necessary, in order to meet floor covering requirements, to cover screeds or slabs with smoothing coats, in order to obtain satisfactory evenness.
More generally, it is well known that, whatever the techniques used, no screed or slab constructed in a traditional manner has all the following three essential characteristics, especially when large surfaces, exceeding 100 or 200 square meters in one block, are involved.
The first characteristic, and without a doubt the most important, concerns hydraulic shrinkage of the slab or screed constructed using the customary cements. For example, it is known that in the case of a totally classical mortar, hydraulic shrinkage is of the order of 1 millimeter per linear meter, in all directions.
This shrinkage, in time, causes microscopic fissures, hairline cracks and other local ruptures or dissociations, which seriously alter the overall mechanical properties of the slab or screed. In actual fact, this problem of shrinkage can be totally catastrophic, particularly in the case of structures with large surface areas, whose mechanical reliability may prove inadequate after the usual guarantee periods have expired, thus causing major losses.
The second characteristic concerns the evenness or level of slabs and screeds, particularly in the event of treatment of large surface areas. This is a result, notably, of the inevitable imperfection of manual application of the paste, whatever tools are used and however great the skill of the professionals concerned.
The third characteristic concerns the smoothing of the slab or screed, to eliminate local imperfections or surface defects.